Patent GB-1187511-A (GB)
Title: Improvements in and relating to Automatic Titration Apparatus
IPC: G01N31/16
Filed: 1967-07-14
Abstract: 1,187,511. Electro-chemical analysis. AJINOMOTO CO. Inc. July 14, 1967 [July 23, 1966; July 25, 1966; Aug. 1, 1966], No.32408/67. Heading G1N. In automatic titration apparatus in which the movement of a sample containing vessel into position, the lowering of the electrode into the sample and the discharge of a standard solution into the sample are all automatically controlled, a fault detector produces an output if the time taken for any of these operations exceeds a predetermined time. As shown the process commences by actuation of motor 8, Fig. 1 driving transporter 9 to bring a sample to be tested into position. Simultaneously motor 12 is energized to operate an electrode controller 11 which allows the electrode 1 to descend, under its own weight, into the sample, the controller 11 transmitting a signal to a driving unit 22 when the electrode is in position. Reception of this latter signal by unit 22 causes energization of motor 14 controlling the discharge of the standard solution into the sample. For each rotation of the motor 14 a fixed volume of the standard solution is ejected into the sample by a piston 17 in cylinder 16, connected to a reservoir 28 of standard solution, which is reciprocated by an eccentric cam 15. The amount of standard solution ejected into the sample is simultaneously monitored by integration at 21 of pulses generated by closure of a switch 20 by knobs 19 on a disc 18 rotating with the cam 15. The knobs are evenly spaced around the disc on that part of its circumference which corresponds to the upward movement of the piston. The voltage on electrode 1 is fed via amplifier 2 to a controller 3 where it is compared with a pre-set voltage indicative of a pH just below the end point of the titration. When this pH is attained, the controller 3 transmits a signal to unit 22 to reduce the speed of the motor 14 which causes a selector 23 to pass the next pulse from switch 20 to a timer 24 causing the motor to be de-energized by unit 25 for a pre-set time after which it is reenergized until the next pulses arrives from switch 20 or the end point is attained. When this latter occurs a signal is transmitted from controller 3 via an end point confirmer circuit 4 to a sequence controller 7 which causes the titration to be stopped, the electrode raised and the next sample to be conveyed into position. Fault detection.- During the process the times taken for the various parts, e.g. the electrode descent, the interval between its descent and the actuation of motor 14 and the transport of a new sample to the measurement position are all monitored by circuit 6 which, if any part is not completed by a pre-set time indicating a fault, causes controller 7 to be operated to de-energize the apparatus and/or actuate alarm 13. Similarly if the volume of standard solution added to the sample exceeds a pre-set amount, set on counter 5, the apparatus is again de-energized. Electrode construction.-The electrode structure comprises a measuring electrode 1, Fig. 8a, and standard, e.g. hydrogen or calomel, electrode 44 closely associated with a standard solution discharge tube 45 and air inlet tube 46 by which the sample is agitated during the titration. The electrode structure is attached to a chain (39, Figs. 6, 7 not shown), engaged round sprockets (42), (42a) and is allowed to fall under its own weight. Modifications.- The duration of the titration may be divided up in to an arbitrary number of parts, the speed of the motor 14 being gradually decreased as the titration end point is approached.